Metal cans or containers, such as aluminum cans to contain beverages, are commonly manufactured by drawing and ironing a circular metal blank into a cylindrical can body having a side wall and a bottom wall. Such cans are then fed into necking and flanging apparatus by transfer or star wheels. Each can enters one of a number of stations in a necking turret undergoing rotational movement which is synchronous with the continued movement of the cans in the star wheel. During this rotational movement, the peripheral edge portion of the can side wall is formed by annular die members or spin forming members to form a neck of reduced diameter at the open end of the can. The necked cans are then transferred via transfer wheels to a flanging turret where the open edge of the can is flanged into a radially outward directed flange suitable for later receiving a can end in a known manner. The arrangement of drawing and ironing machines for forming the can bodies, and machines containing necking and flanging turrets are well known in the art.
A plurality of flanging heads are typically circumferentially spaced at the periphery of the flanging turret. Each flanging head has plural flanging rollers or spinners freely rotatably supported about their respective longitudinal axes in a central housing or cage. The cage is rotatable about its central longitudinal axis so that the flanging rollers revolve therearound in planetary relationship during flanging. Each flanging head typically includes an outer housing formed with a mounting flange adapted to be bolted to a mounting disk attached to the flanging turret, as is well known. The central housing containing the flanging rollers is rotatably disposed in the outer housing with ball bearings. A splined shaft projecting rearwardly from the outer housing is attached to the central housing to impart rotational movement about the central longitudinal axis via meshing contact with gearing disposed within the flanging turret.
The front of the flanging head is defined by a stop ring 100 (depicted in prior art FIG. 3) bolted to the outer housing. A retainer plate sandwiched between the stop ring and ball bearing elements assists in maintaining the forming surface 120 of each flanging roller 140 in operative alignment with the stop surfaces 160 on the stop ring 100. As the flanging heads rotate, the marginal necked portion 180 of the can is advanced into contact with the rotating cluster of flanging rollers 140. Since the can does not rotate, contact between the marginal end 180 with the revolving rollers 140 induces free rotation of each roller which results in spinning contact and flange formation as the open end of the can contacts the progressively larger diameter portions 200 of each roller. These progressively larger diameter portions 200 cause corresponding enlargement of the can end and deflection of the metal into a flange 220 extending approximately perpendicular to the longitudinal axis of the can.
As the formed flange 220 is in its final forming stages during final camming movement of the can against the rotating rollers 140, the flange end contacts the stop surfaces 160 of the stationary stop ring 100, whose purpose is to stop the flange 220 at a specific preselected diameter so that the flange has the same width along all sides of the can. In practice, however, the annular flange 220 usually strikes one side of the surface 160 before it hits all sides. When this happens, it usually takes only a small additional force to disadvantageously force the flange into the crack 240 formed between the rotating roller 140 and the stationary stop ring 100. When this occurs, the can is ruined and must be scrapped, since the metal forced into the crack 240 forms a sharp vertical ear on the can flange 220.